Implantable medical devices (IMDs) are used to treat many conditions. IMDs devices such as pacemakers and defibrillators include electronics mounted within a housing. The electronics are typically operatively connected to a lead or leads, which can be implanted in or about the heart. The leads implanted in or about the heart can be used to reverse certain life-threatening arrhythmias, or to stimulate contraction of the heart. Electrical energy is applied to the heart via electrodes on the leads to return the heart to normal rhythm.
An electrical feedthrough can be used in an IMD to provide an isolated electrical path from an exterior of the IMD to an interior of a housing. Feedthroughs can be used with housings that are sealed, such as biocompatible, hermetically sealed housings. To preserve internal components, the feedthrough can be leak-resistant. Some feedthroughs are biocompatible and hermetically sealed. Some IMDs using such hermetically sealed feedthroughs can protect implanted electronics from body fluids and can resist undesirable exposure of the patient to materials from inside the housing.
To provide such an electrical feedthrough, a ferrule (or mechanical element) can be disposed through the housing and coupled to the housing. A conduit or member that is able to conduct electricity can extend through the ferrule. An electrical insulator, such as being formed from a ceramic material, can be disposed between the ferrule and the electrically conductive conduit. The conduit and the insulator can have a braze joint therebetween, and the ferrule and the insulator can have a braze joint therebetween, which both hermetically seal the conduit and the ferrule with the insulator. A hermetically sealed, electrical feedthrough configured as such can maintain hermeticity of the housing while allowing an electrical signal to enter or exit the housing.